diff --git a/RPi/i2c_challenge.c b/RPi/i2c_challenge.c
index 6b92a05..679cac8 100644
--- a/RPi/i2c_challenge.c
+++ b/RPi/i2c_challenge.c
@@ -17,6 +17,7 @@
 ***********************************************************
 */
 
+#include <stdint.h>
 #include <stdio.h>
 #include <wiringPi.h>
 #include <wiringPiI2C.h>